The aim of this study was to determine the baseline pattern of resistance to aminoglycosides in a medical intensive care unit and to evaluate the influence on resistance rates of the use of amikacin as first-line aminoglycoside. A prospective bacteriological surveillance study was done during a 3-month baseline period with all aminoglycosides freely available, followed by a 9-month study period with predominant amikacin use. All patients admitted for more than 24 hours who were colonized or infected were included. Susceptibility rates for all isolates during the baseline period were 69% for amikacin, 32% for gentamicin, 35% for tobramycin and 46% for netilmicin. During the amikacin study period susceptibility rates rose to 75%, 43%, 44% and 51%, respectively. The increase in susceptibility to gentamicin and tobramycin, considering all isolates, was statistically significant. There was also a significant increase in susceptibility to netilmicin for gram-negative bacteria. There was no significant change in susceptibility to amikacin. We conclude that the use of amikacin as a first-choice aminoglycoside in a medical intensive care unit is warranted because of the better susceptibility rates and does not lead to a rapid rise in amikacin resistance. The predominant use of amikacin may have a favorable influence on susceptibility to the other aminoglycosides. To answer the question of whether these conclusions will remain valid over a longer period of predominant amikacin use, follow-up surveillance studies are mandatory.